"'...I know the concept. South wins the Civil War, Hitler wins World War Two, that sort of thing. Been some pretty good movies that used it.'" (p. 177)
There are other obvious themes:
Alexander the Great lived longer (Poul Anderson, Greg Bear, SM Stirling);
different outcomes in 1066 (?);
no Reformation (Kingsley Amis, Philip Pullman);
a successful Spanish Armada (Keith Roberts);
Oliver Cromwell lived longer (a DC Comics Elseworld) -
-and less obvious:
aliens invaded Earth during World War II (Harry Turtledove);
Mars and Venus were terraformed long ago (SM Stirling);
someone discovered how to degauss the effects of cold iron (Poul Anderson).
Bring The Jubilee by Ward Moore begins as a Confederate States alternative history but ends as a causality violation time travel novel, thus showing the degree of overlap between these two sf themes. Did Bring The Jubilee influence Anderson's "Time Patrol"? Anderson could not remember. However, conceptually, Bring The Jubilee does belong in a sequence of precursors to the Time Patrol:
Mark Twain, A Connecticut Yankee...;
HG Wells, The Time Machine;
L Sprague de Camp, Lest Darkness Fall;
Moore, Bring The Jubilee;
Anderson, "The Little Monster" and "The Man who Came Early."
An involuntary time traveler prospers and makes changes that do not last;
the Time Traveler invents the Time Machine and his dinner guests discuss anachronisms on battlefields like Hastings;
a second involuntary time traveler prospers and makes lasting changes;
a time traveling historian unintentionally diverts the course of a decisive battle;
a third involuntary time traveler survives but a fourth comes to grief;
the Time Patrol is founded to prevent accidental or deliberate historical changes.
In Anderson's "The House of Sorrows" and also in the deleted timeline of his "Delenda Est," Christianity does not get started whereas, in his Westfall timeline, Christendom exists but is destroyed. In all three timelines, Europe remains divided into small warring states practicing polytheism. The difference is that the Westfallers eventually develop science.
